Louis cohen



Dec. 26, 1922. v

L-. COHEN.

ELECTRICAL S!6NA'LING.

FILED JUNE 29 I921 gwoentoa Lou/s Cohen Patented Dec. 26, 1922..

earn LOUIS COHEN, OF WASHINGTON, DISTRICT OF COLUMBIA.

ELECTRICAL SIGNALING.

Application filed June 29, 1921. Serial 1%. 481,840.

To all whom it may concern:

Be it knowntthat I, LOUIS COHEN, a citizen of the United States,residing at Vfashington, in the District of Columbia, have invented a certain new and useful. Improve ment in Electrical Signaling, of which the following is a specification. I

This invention relates to the art of elec trical signaling, particularly, receiving radio signals, and a system for use in practicing the same.

The object of the present inventionis to eliminate interferences in the reception of radio signals and thus insure greater reliability in radio communication. I

It is well known that inthe present prac tics of radio signaling, interferences from other stations are not entirely eliminated. lVhen the difference in the frequencies be tween the signals to be received and the in terfering signals is small, the various tuning arrangements now generallynsed in present practice are not effective in completely eliminating the interference effects. In this invention, a new methodis used by which a higher degree of selectivityis obtained.

In carrying out the invention,-the incoming signals are acted upon by local oscillations which combine with them producing beats; The beat frequency current is then impressed upon a Wheatstone bridge, the constants of the arms of which are so act justed as'to produce zero potential. across the bridging arm for the current of the beat frequencyyand hence no current flow in it.

.The indicating instrument is coupled to two arms of the bridge and also to the bridging arms. I By properly adjusting the couplings in the matter of direction and magnitude, a condition is obtained where the interference effects'are'balanced out, and the indicating instrument responds only to the signals which are to be received,

The principle of operation can be better ing beats with the incoming signals. The beat frequency currentfiowing in plate circuit 9 is impressed through the secondary 10 of transformer 8 and the WVheatstone bridge at the points 11,12. The four arms of the bridge, a, Z), 0, d, consisting of inductances and capacities 13, 1a; 15,16; 17, 18; 19, 20; respectively, are so adjustedas to ob tain an exact balance for the beatfrequency current on the bridging arm 21, hence no current flow in it. The beat frequencycurrent, however,in passing through the bridge arms 6 andd, induces E. M. F.s in the secondaries 24, 26, and by properly connecting the secondaries 24, 26 the effects are made additive and thus, set up a current flow in the circuit 22, 24:, 28, 26 which affects the indicator 28. For currents of different frequencies the bridge is no longer balanced and there will be, therefore, a current flow in the bridging arm2l. By properly ad justing the transformers 28, 25 and 27 in respect to magnitude and direction, a condi tion is obtained whereby the E. M. F.s inducedin the secondary 22 of transformer 23 neutralize the resultant E. M. F.s induced in the secondaries 2a and 26 of-tran'sformers 25 and 27 respectively, and there- We may take the followingexample in illustrating the operation of this invention. Suppose the bridge arms of the l/Vheatstone bridge are adjusted for balance at the fre .quency of 500; vIf it is desired to receive a signal at a frequency of 50,000,the local oscillator is adjusted to produce oscillations of frequencies either 50,500 or 419,500, so that in either case a beat frequency of 500 isobtained, and for that beat frequency cur rent the bridge iscompletelybalanced, no

current flow in the bridging-arm 21, and.

hence the E. M. F.7s induced in the secondaries of transformers 25 and 27 set up a current flow intheindicator circuit affecting the indicator. If, however, an interfering signal of slightly different frequency, say

50,100, acts on the antenna, the beats produced with the local oscillations in this case with be either 400 or 600, and in either case the balance of the bridge is upset, setting up a current flow in the bridging arm 21 which may be made, by properly adjusting its secondary, to neutralize the E. M. F.s induced .in the secondaries of the other two trans,-

Iformers 25 and 27, and hence render the indi of the interfering signal. It is seen, there- :iore, that 3501' this arrangement the interi'erence effects for, such a smalldiliierence, out frequencyas 1 in 50,000 or one-firth of one per cent, may be completely eliminated. It is obvious that various modifications of the circuit arrangementniay be made with,

out departing from the spirit of the invention. Any method :for generating local oscillations, or any -means employed to rectify the high frequency oscillations clearly comes Within the scope oi? this invention; The diagram and description given here shows only a typical embodiment of the invention illustratin the underlying principles governing its operation.

I claim: a 1. An improvement in radio signaling, comprising an antenna system and secondary oscillating circuit coupled to thesaid antenna I system, ineans for generating local oscillarent bein otions in said secondary oscillating circuit,

said local oscillations combining With the high frequency currents flowing in the antenna and producing beats, said beats curdelivered to a VVheatstone bridge, an indicator being connected in a circuit Whichds electrically associated With two arms and the bridging arm of the said "Wheatstone bridge;

2. Radio signaling apparatus comprising an antenna system and secondary oscillating circuit coupled to the said antenna system,

' a three electrode vacuum tube detector including a regenerative coil operatlvely assooiated With'the' secondary oscillating circuit for producing oscillations in the said secondary circuit, said oscillations combining With the incoming signalsand producv ing beats, said beat current bein delivered heatstone through a transformer to .a bridge, the arms of said Wheatstone bridge being adjusted to obtain a balance on the bridging aring-an indicator being connector to a circuit which is coupled to two arms of thebridge and the bridging arm of the said "Wheatstone bridge.

3. An improvement in radio signaling, comprising an antenna system and secondary oscillating circuit coupled to the said antenna system, means for generating local oscillations in said secondaryoscillating circuit, said local oscillations combining with" hi0? circuit free from the disturbing effect the high'frequency currents fiowingin the antenna and producing beats, said beat cur-- rent being delivered to a Wheatstone bridge,'an inclicator being connected to a circuit which is coupledtotwo arms of the bridgeand the bridging arm of the said,

Wheatstone bridge.

4. An improvement in radio signaling, comprising an antenna system and secondary oscillating circuit coupled to the said antenna tenna s stem means *for eneratin local 7 y a a oscillations in said secondary oscillating circu1t. said lOCtLlOSClllZLtlOIlS combining with the high frequency signal currents flowing in the antenna and producing beats, said beat currents being delivered through a tIZLIlSfOXIDBI toa Wheatstone bridge, the

arms of said Wlieatstone bridge, being ad justed to obtain a balance on the bridging arm for the said heat currents; an indicator being connected to a circuit which is coupled to two arms of the bridge, and the bridging arm of the said Wheatstone bridge. I V

6.,Radio signaling apparatus comprising an antenna system and secondaryoscillating circuit coupled to the said antenna =system, a three electrode vacuum" tube detector includinga regenerative coil 'operatively associated With said secondary OSClllEttlIlg circuit for producing oscillations in the said secondary circuit, said oscillationscoinbining with the incoming signals and producing beats, alVheatstone bridge tor receiving the beat current,uthe arms of sa1dWheatstone bridge ;,being adjusted to obtain a balance on the bridgingarm; and a y-1m;

dicator connected in a circuit coupled to tWo arms of-the bridge and theflbridging arm of thesaidrVVheatstonefbridge;

Louis conniif r 

